Diffusion pump



April 8,1969 w. 5. BACHLER ET AL 3,437,261

DIFFUSION PUMP Filed April 5, 1967 |2 5s I g 46 48 '6 "WP mn '1' 4o 7 38 59 36 I llll 4| m I @129 24 37 2| r22 s5 s3 /"g V l 76 l 62 75 FIGURE] WERNER G. BACHLER HANS GEORG-NOLLER BY M ATTORNEY INVENTORS United States Patent US. Cl. 230-101 7 Claims ABSTRACT OF THE DISCLOSURE A diffusion vacuum pump of conventional structure including a boiler at the bottom thereof for heating the pump fluid such as oil. The bottom plate of the boiler is designed to have attached to it, in intimate heat transfer relation, either a heating unit or a cooling unit. The cooling unit, in turn, is so designed that it may have intimately attached to it the heating unit; thereby defining a structure wherein a cooling unit is sandwiched between the bottom plate of the boiler and the heating unit, all of these units being assembled in intimate heat transfer relation. Alternatively, the cooling unit may be omitted from the assembly.

Background 07 the invention In some applications where diffusion vacuum pumps are used, it is desirable to quickly vent the chamber to atmosphere after the chamber has been evacuated by the vacuum pump. If this is done while the working chamber is still connected to the diffusion pump, there will be re sultant dissociation or contamination of the pump fluid which is still being vaporized. In such installations, then it is necessary either to close communication between the evacuated chamber and the diffusion pump by means of a disc valve, or the pump may be first cooled off to a level such that the air may be admitted to the diffusion pump without danger of the dissociation of the fuel. It is desirable, of course, that the cooling unit provided for this purpose be efiicient in the sense that it provide rapid cooling of the pump fluid in order to reduce the cycle time in operations which require intermittent evacuation and venting to atmosphere of a working chamber.

It is known to build various types of cooling units into diffusion pumps, which units necessarily add to the cost of these pumps. An inherent disadvantage of having the cooling unit built into the pump is that, in the event of failure of the cooling unit, the entire pump must be taken out of service and repaired; and the addition of this cooling structure to the pump will likely add to the down time for service. Another factor to be considered is that there are many applications of diffusion pumps wherein the rapid cooling of the pump is not required. This means that manufacturers of diffusion pumps may have to provide two standard pump for each given size, one not including a cooling system and one including a cooling system.

It would be desirable, then, to provide a diffusion pump structure wherein a cooling unit can be attached to the pump where desired, to provide a rapid cooling feature, and wherein the cooling unit can be omitted from the pump where rapid cooling of the pump is not required.

Summary of the invention An object of the invention is to provide a diffusion vac- 'uum pump structure including detachable heating and cooling units either or both of which may be readily attached to the pump in efficient heat transfer relation. According to the invention, the bottom plate of the diffusion pump boiler includes means for intimately attaching thereto either a cooling unit or a heating unit. The heating unit,

Patented Apr. 8, 1969 which may consist of electric heat-ing coils embedded in a suitable plate of heat conductive material, may be attached directly to the boiler bottom plate by means of screw fasteners which secure the heating plate to the boiler plate in intimate heat transfer relation. Alternatively, a cooling unit, which may consist of a cooling coil embedded in a suitable plate of heat conductive material, may be secured to the boiler plate in the same manner; the abovementioned heating plate then being secured to the cooling plate in the same intimate heat transfer relation by means of threaded fasteners.

Brief description of the drawing FIG. 1 is a vertical sectional View of a diffusion vacuum pump according to the present invention; and

FIG. 2 is a sectional view of the cooling unit taken along the line 22 of FIG. 1 looking in the direction of the appended arrows.

Description of the preferred embodiment Referring to the drawing, there is shown a diffusion vacuum pump having a cylindrical housing 12, the upper end thereof defining a flanged inlet opening 13 adapted for connection with a working chamber (not shown) which is to be evacuated. The flanged tubulation 14 which projects from the lower portion of the pump housing 12, is adapted for connection to a conventional vacuum force pump (not shown). Spaced from the lower end of the pump housing 12 is a transverse bottom plate 15, integrally attached to the housing 12, which defines the supporting means for other portions of the pump to be described. A hollow cooling coil 16 is attached in intimate heat transfer relation to a portion of the exterior surface of the housing 12; and is provided with means for connection to a source of cooling fluid for the purpose of cooling portions of the housing wall during op eration of the pump.

The internal elements of the diffusion pump include a base 21 defined by a lower cylindrical wall section 22 and an upper reduced diameter cylindrical wall section 23. The lower cylindrical wall 22 is supported directly on the base plate 15 and defines, with the base plate 15, the boiler which contains a suitable pump fluid such as oil.

The several jet nozzle assemblies defining the four stages of the diffusion pump are supported on an upwardly extending column 24, which is secured by means of brackets 25 to the upper cylinder section 23 of the base 21. The first, or bottom, nozzle 26 is formed by the base 21 and the hollow, generally cylindrical element 27. The element 27 includes a downwardly extending cylindrical wall 28, an upwardly extending cylindrical wall 29, an intermediate outwardly and downwardly extending lip 30, and brackets 31 by means of which the element is secured to the column 24. More particularly, then, the first nozzle 26 is formed by the upwardly extending cylindrical wall 23 of the base 21 and the lip 30 of the element 27, defining an annular nozzle which directs pump fluid vapor downwardly and toward the inner wall surface of the housing 12. The cylindrical walls 23 and 28 define an annular passage for directing the vapor to the nozzle 26.

A second hollow, generally cylindrical element 36 consists of a downwardly extending cylindrical wall 37, an upwardly extending cylindrical wall 38, an intermediate and outwardly extending lip 39, and brackets which secure the element 36 to the column 24. The cylindrical walls 29 and 37 define an annular passage for directing pump fluid vapor to the second nozzle 41, which is defined by the cylindrical wall 29 and the lip 39.

A third hollow, generally cylindrical element 46 is supported on the column 24 by means of suitable brackets,

and consists of a downwardly extending cylindrical wall 47, an upwardly extending cylindrical wall 48, and an intermediate downwardly and outwardly extending lip 49. The cylindrical wall 47 is received within the cylindrical wall 38; and these walls define an annular passage for directing pump fluid vapor to the third stage nozzle 51 defined by the cylindrical wall 38 and the lip 49.

A cup shaped cap 55 is secured to the upper end of the column 24, and defines a downwardly and outwardly extending lip 57 which overlies the cylindrical wall 48 and defines therewith the upper or fourth stage nozzle 58.

The above described structure of a four stage diffusion pump is known; and these described details of the pump structure, as such, define no part of the present invention.

As shown in the drawing, a cooling unit 61 is detachably secured immediately beneath the base plate of the pump. As best shown in FIG. 2, this cooling unit consists of a circular metallic plate 62 in which a cooling coil tubulation 63 is embedded, the two ends of the cooling coil projecting from the periphery of the plate 62 and adapted to be provided with suitable fittings for coupling to a source of cooling fluid. The cooling coil tubulation is embedded, or otherwise secured, intimately to the plate 62 for the purpose of providing maximum heat transfer between the tubulation and the plate. The plate is fabricated from a material having good heat conductivity, and is designed to transfer heat efficiently from the base plate 15 to the coil 63 and also between the heating unit, to be described, and the base plate 15.

The cooling plate 62 is secured to the pump base plate 15 by means of three cap screws 65, for example, which pass through apertures 64 in the plate and are threaded into bores in the base plate 15. Since the base plate 15 should be quite thin to present minimum resistance to heat transfer between the cooling unit and the fluid in the boiler the base plate is provided with suitable upwardly extending bosses 17 to provide sufficient material to be bored and threaded to receive the cap screws. The threaded bores in the base plate are preferably equally spaced on a concentric circle about the central axis of the pump three such bores being indicated in the drawing. Of course the bores 64 in the cooling plate 62 are arranged to be aligned with the threaded bores in the base plate 15.

The plate 62 of the cooling unit is provided with three additional bores 66 which are threaded to receive cap screws. These bores are perfectly arranged on the same circle as the bores 64 and are equally spaced from each other and between the bores 64.

As shown in the drawing a heating unit 71 is secured immediately beneath the cooling unit 61. The heating unit 71 also consists of the circular metallic plate 72; this plate being formed of a good heat conductive material and having embedded therein one or more electrical conductors for electrically heating the plate 72. Suitable terminations 74 for the conductor are provided externally of the plate 72 for connecting the conductor to a suitable source of electric power. The heating plate 72 is provided with three bores 75 arranged on a circle concentric with the center of the circular heating plate and having the same radius as the circle which locates the bores 64 and 66 for the cooling plate 62. Also these bores 75 are equally spaced from each other so that when the heating unit 71 is assembled to the cooling unit 61 the bores 75 will be aligned with the threaded bores 66 and the heating plate is attached to the cooling plate by means of cap screws 76.

In a sandwich relation then the cooling plate 62 is assembled in heat transfer relation to the pump base plate 15 and the heating plate 72 is assembled in heat transfer relation to the cooling plate 62.

In the operation of the above described assembly the pump fluid (oil for example) is heated in the pump boiler 22 by means of the heating unit 71. The heat provided by the heating unit is transmitted through the cooling unit 61 and through the pump base plate 15 to the pump fluid; and for this reason as above described the cooling plate 62 and the pump base plate 15 should be constructed of a material and otherwise designed for maximum heat transfer to provide for the fastest possible heating of the pump fluid. In applications requiring quick cooling of the diffusion pump the heating unit is shut off and cooling fluid is circulated through the tubulation 63 of the cooling unit 61. Here again as above described the units are designed for maximum heat transfer; in this case the heat flowing from the pump fluid through the pump base plate 15 and through the cooling plate 62 to the tubulation 63.

In applications where rapid cooling of the pump is not desired the above described diffusion pump may be assembled without the cooling unit 61; that is the heating unit 71 may first be removed from the cooling unit 61 and the cooling unit 61 may then be removed or detached from the base plate 15. Due to the above described arrangement of the bores in the various elements the heating unit 71 may then be attached directly to the base plate 15; the bores being in proper alignment with the bores in the base plate 15. Assembled in this manner, the pump heating unit should be somewhat more efficient since the heat will not have to transfer through the additional plate 62 of the cooling unit.

What is claimed is:

1. A diffusion vacuum pump apparatus including a pump housing defined by a cylindrical wall portion and a bottom wall, said housing having inlet and outlet openings, a boiler for pump fluid formed within said housing adjacent to said bottom wall, and one or more nozzles for directing pump fluid vapor toward said housing wall;

wherein the improvement comprises the combination therewith of a cooling unit and a heating unit, and fastening means comprising first and second co-acting fasteners for attaching said units to said housing; said housing bottom wall having a plurality of first fasteners in a predetermined arrangement and each of said units having the same plurality of second fasteners in the same predetermined arrangement for detachably securing either of said units to said housing bottom wall in intimate heat transfer relation; and one of said units having the same plurality of first fasteners in the same predetermined arrangement for co-acting with the second fasteners of the other unit for detachably securing said other unit to said one unit in intimate heat transfer relation.

2. A diffusion vacuum pump apparatus including a pump housing defined by a cylindrical wall portion and a bottom wall, said housing having inlet and outlet openings, a boiler for pump fluid formed within said housing adjacent to said bottom wall, and one or more nozzles for directing pump fluid vapor toward said housing wall;

wherein the improvement comprises the combination therewith of a cooling unit and a heating unit detachably secured to said housing bottom wall and to each other in intimate heat transfer relation therewith; said bottom wall, said cooling unit, and said heating unit being constructed in a manner that either said cooling unit or said heating unit may be detachably secured to said bottom wall in intimate heat transfer relation therewith, and that one unit may be detachably secured to the other in intimate heat transfer relation therewith;

said cooling unit and said heating unit each comprising a platelike member; said bottom wall being provided with a plurality of fastening means having a predetermined arrangement relative to the center thereof; one of said plates being provided with the same plurality of similar fastening means having the same predetermined arrangement relative to the center thereof; said one plate being provided with the same plurality of bores having the same predetermined arrangement relative to the center thereof, but rotated 6. A diffusion vacuum pump apparatus according to relative to said fastening means; the other of said claim 5 plates being provided with the same plurality of bores wherein said threaded bores in the bottom wall are having the same predetermined arrangement relative to the center thereof;

ing through the bores of said other plate to secure said other plate to said one plate.

3. A dilfusion vacuum pump apparatus according to arranged on a circle in equally spaced relation to each other; wherein said threaded bores in said cool said bottom wall fastening means co-acting with com- 5 ing plate are arranged on a circle of the same radius plementary fastening means passing through the and equally spaced from each other; wherein said bores of either of said plates to secure the plate to larger bores in said cooling plate are arranged on said bottom wall; said one plate fastening means the same circle and equally spaced from each other, co-acting with complementary fastening means pass- 10 said larger bores being positioned between said threaded bores of said cooling plate; and wherein larger bores in said heating plate are arranged on a circle having the same radius and equally spaced from each other. 7. A diffusion vacuum pump apparatus according to claim 3 wherein said threaded bores in the bottom wall are claim 2 wherein said plurality of fastening means associated with said bottom wall and with said one plate comprise a plurality of threaded bores having the defined predetermined arrangement relative to the centers thereof; and wherein said complementary fastening means comprise threaded fasteners passing through said first mentioned bores in said one plate and in said other plate, said first mentioned bores being larger than said threaded bores.

arranged on a circle in equally spaced relation to each other; wherein said threaded bores in said one plate are arranged on a circle of the same radius and equally spaced from each other; wherein said larger bores in said one plate are arranged on the same circle and equally spaced from each other,

said larger bores being positioned between said threaded bores of said one plate; and wherein said larger bores in said other plate are arranged on a circle having the same radius and equally spaced from each other.

4. A diffusion vacuum pump apparatus according to claim 2 2 wherein said one plate is the plate-like member of said cooling unit; and wherein said other plate is the plate-like member of said heating unit.

5. A diffusion vacuum pump apparatus according to claim 2 wherein said one plate is the plate-like member of said cooling unit; wherein said other plate is the plate- References Cited UNITED STATES PATENTS like member of said heating unit; gsg g et a1 wherein said plurality of fastening means associated 3258196 6/1966 Knox 1: with said bottom wall and with said one plate com- 33O2864 2/1967 Nicholas 230 101 prise threaded bores having the defined predeter- 3332608 7/1967 L df 230 101 mined arrangement relative to the centers thereof; 3360188 12/1967 g f 1 and wherein said complementary fastening means comprise threaded fasteners passing through the first mentioned bores in said one plate and in said other plate, said first mentioned bores being larger than said threaded bores.

40 DONLEY J. STOCKING, Primary Examiner. WARREN J. KRAUSS, Assistant Examz'nler. 

